• Journal of the Korean Society of Food Science and Nutrition
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• v.45 no.2
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• pp.277-283
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• 2016

To improve the microbiological safety of wild vegetables after harvest, Aster scaber and Cirsium setidens Nakai were treated with combinations of 50 ppm aqueous chlorine dioxide ($ClO_2$)/0.5% citric acid or fumaric acid, and 50 ppm $ClO_2$/0.5% fumaric acid/blanching at $90^{\circ}C$ for 2 min. Combined treatment of 50 ppm $ClO_2$ and 0.5% citric acid reduced populations of total aerobic bacteria, yeast, and molds in Aster scaber and Cirsium setidens Nakai by 2.80~3.64 and 2.02~2.67 log CFU/g, respectively, compared to those of the control. Combined treatment of 50 ppm $ClO_2$ and 0.5% fumaric acid reduced total aerobic bacteria, yeast and molds populations by 3.62~3.82 and 2.47~3.02 log CFU/g, respectively. Based on the results, combined treatment of $ClO_2$ and fumaric acid was more effective in controlling microorganisms in the wild vegetables than either $ClO_2$ or citric acid. In addition, combined treatment of $ClO_2$/fumaric acid/blanching reduced the populations of total aerobic bacteria by 4.59~5.12 log CFU/g, and populations of yeast and molds were not detected by treatment. These results suggest that combined treatment of $ClO_2$/fumaric acid/blanching is the most effective method for improving microbiological safety of wild vegetables after harvest.

• 한국균학회소식:학술대회논문집
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• 2014.10a
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• pp.25-25
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• 2014

Three species of Fusarium, F. fujikuroi, F. verticillioides and F. proliferatum, are known to be associated with bakanae disease of rice [1, 2]. F. fujikuroi infects rice flowers and survive in endosperm and embryo of the seeds. Infected seed is an important source of primary inoculum of pathogens [3]. Seeds of rice (Oryza sativa cv. Boramchan) collected from bakanae-infected field were found to be 96% infected with Fusarium sp., 52% with F. fujikuroi, 42% with F. verticillioides, and 12% with F. proliferatum as determined by incubation method and species-specific PCR assays. F. fujikuroi was detected at lemma/palea, endosperm and embryo whereas F. verticillioides and F. proliferatum were recovered only from lemma/palea by means of component plating test. Seed disinfection methods have been developed to control bakanae disease and prochloraz has been most widely used for rice seeds. Two chemicals formulated with prochloraz (PC 1) and prochloraz + hexaconazole (PC 2) that inhibit biosynthesis of ergosterol strongly reduced the incidence of Fusarium spp. on selective media to 4.7% and 2.0%, respectively. Disease symptoms of rice seedlings in nursery soil were alleviated by chemical treatment; seedlings with elongated leaves or wide angle between leaf and stem were strikingly reduced from 15.6 to 3.2% (PC 1) and 0 (PC 2), stem rots were reduced from 56.9 to 26.2% (PC 1) and 32.1% (PC 2), and normal seedling increased from 0.4 to 13.3% (PC 2). Prochloraz has some disadvantages and risks such as the occurrence of tolerant pathogens [4] and effects on the sterol synthesis in animals and humans [5]. For these reasons, it is necessary to develop new disinfection method that do not induce fungal tolerance and are safe to humans and animals. Chlorine dioxide ($ClO_2$), that is less toxic, produces no harmful byproducts, and has high oxidizing power, has been reported to be effective at disinfection of several phytopathogenic fungi including Colletotrichum spp. and Alternaria spp. [6]. Gaseous $ClO_2$ applied to rice seeds at a concentration of 20 ppm strongly suppressed mycelial growth of Fusarium fujikuroi, F. verticillioides and F. proliferatum. The incidence of Fusarium spp. in dry seed with 8.7% seed moisture content (SMC) tended to decrease as the concentration of $ClO_2$ increased from 20 to 40 ppm. Applying 40 ppm $ClO_2$ at 90% relative humidity, incidence was reduced to 5.3% and resulted in significant reduction of disease symptoms on MS media. In nursery soil, stem rot was reduced from 56.9 to 15.4% and the number of normal seedlings increased from 0.4 to 25.5%. With water-soaked seeds (33.1% SMC) holding moisture in the endosperm and embryo, the effectiveness of disinfection using $ClO_2$ increased, even when treated with only 20 ppm for four hours. This suggests that moisture was a key element for action of $ClO_2$. Removal of the palea and lemma from seeds significantly decreased the incidence of Fusarium spp. to 3.0%. Seed germination appeared to decrease slightly by water-soaking at $30^{\circ}C$ because of increased SMC and by physical damage of embryos from hulling. These results indicate that the use of gaseous $ClO_2$ was effective as a means to disinfect rice seeds infected with Fusarium spp. and that moisture around the pathogens in the seed was an important factor for the action of $ClO_2$. Further investigations should be conducted to ascertain the best conditions for complete disinfection of Fusarium spp. that infect deep site of rice seeds.

• Transactions on Electrical and Electronic Materials
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• v.1 no.2
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• pp.1-6
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• 2000

This article presents the experiments and considerations possible about gate etching in polysilicon when oxygen gas is added in chamber, We propose the novel study with optical emission spectroscopy in polysilicon etching. It is shown that added oxygen gases play an important role in enhencement of density in chlorine gases as a scavenger of silicon from SiCl$\_$x/. And a small amount of Si-O bonds are deposited and then the deposited thin film protect silicon dioxyde against reaction chlorine with silicon in SiO$_2$. Consequently, we can improve the selectivity of polysilicon the silicon dioxide, which is clearly explained in this model.

• The Korean Journal of Food And Nutrition
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• v.27 no.5
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• pp.881-887
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• 2014

To prolong the shelf-life of domestic peaches, samples were treated with 30 ppm of aqueous chlorine dioxide ($ClO_2$) for 0~15 minute, after which the spoilage rate, changes in physico-chemical and sensory properties of treated samples were investigated. The control showed spoilage at day 4, and then 31.25% of control showed spoilage at day 8. However, samples treated with aqueous $ClO_2$ had no spoilage at day 4. On day 6, only 6.25% of samples treated with aqueous $ClO_2$ for 5 min showed spoilage. After 8 days, no spoilage was observed for samples treated with aqueous $ClO_2$ for 10 and 15 min. The weight change of the control was higher than that of aqueous $ClO_2$ treated samples for 8 days of storage. There were no differences in pH of samples among the treatments, but they were increased by storage time. Although there were no initial differences in the firmness of samples among the treatments, firmness of the control sample was decreased faster than those of the aqueous $ClO_2$ treated samples for 8 days of storage. No significant changes in lightness, redness and yellowness of the samples by aqueous $ClO_2$ treatment were observed during storage. The sensory parameters including taste, flavor, color, texture and overall acceptance at the initial period were not different among treatments. However, all scores of the control were decreased faster than those of aqueous $ClO_2$ treated samples during storage.

• The Korean Journal of Malacology
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• v.28 no.2
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• pp.125-129
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• 2012

The study describes growth and survival on different kinds of sediment improvements of early spats of the hard clam, Meretrix petechialis. Specimens of the mature hard clam were collected in the intertidal zone of Yeonggwang, Korea, July 2011. After transportation, early spats(shell length $196{\pm}14{\mu}m$) collected in mature hard clam were used. Experiment period were July 7 to August 6 in 2011 (30 days). Sediment improvements used iodine(10 ppm), hydrogen peroxide($H_2O_2$, 5 ppm), sodium hypochlorite (NaClO, 100 ppm), chlorine dioxide($ClO_2$, 100 ppm) and potassium permanganate ($KMnO_4$, 5 ppm). After cultured during 30 days, shell length growth of hard clam were observed $1.04{\pm}0.26mm$ in sodium hypochlorite 100 ppm, $1.03{\pm}0.25mm$ in chlorine dioxide 100 ppm and $1.01{\pm}0.28mm$ in iodine 10 ppm. Survival rate were 31.4% in chlorine dioxide 100 ppm, 12.1% in sodium hypochlorite 100 ppm, 11.6% in iodine 10 ppm, 1.5% in hydrogen peroxide 5 ppm and 0% in potassium permanganate 5 ppm.

• Journal of Animal Environmental Science
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• v.17 no.sup
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• pp.43-50
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• 2011

This study was conducted to verify the effect of chlorine dioxide ($ClO_2$) on odor reduction at a commercial swine facility consisting of a windowless piglet barn and a grower/fattening barn. The windowless piglet barn used a duct ventilation system. Air velocity at very below the upper duct was 4.53 m/s. Air velocity at the lower space around the living space of pigs in the grower/fattening barn was 0.26 m/s. $NH_3$ concentration was around 9ppm and less than 3 ppm before and after the $ClO_2$ spraying, respectively, which was over 70% reduction. There was no $H_2S$ detection. $NH_3$ concentrations measured in the windowless grower/fattening barn and at the exhausted air were 26 ppm and 11ppm, respectively. $NH_3$ concentration at a biocurtain outside was less than 1 ppm. Hence, $ClO_2$ spraying at windowless barns was effectively decreased malodor such as $NH_3$.

• Food Science and Biotechnology
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• v.17 no.5
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• pp.971-975
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• 2008

This study was to examine the potential disinfection efficiencies of 10 compounds by determining their antimicrobial capacity and ichthyotoxicity. Antimicrobial effects against Vibrio sp., Edwadsiella tarda, Streptococcus sp., and Staphylococcus sp. were tested using 10 different disinfectants; hydrogen peroxide, sodium hypochlorite, chlorine dioxide, povidon iodine, formaldehyde, glutaraldehyde, quaternary ammonium compounds (QACs), didecyl dimethyl ammonium chloride (DDAC), ortho-dichlorobenzen, and copper sulfate. Chlorine dioxide ($ClO_2$) containing 5% $ClO_2$ and copper sulfate had no effects on bactericidal activity, while the other disinfectants resulted in 99.99% bactericidal activity against 4 strains of fish pathogenic bacteria. The ichthyotoxicity of the 10 disinfectants was investigated using 3 kinds of fish species; flounder (Paralichthys olivaceus), rockfish (Sebastes pachycephalus), and black sea bream (Acanthopagrus schlegelii). Median lethal concentration ($LC_{50}$) values of the 10 disinfectants were estimated to determine toxicity ranges of the doses within 24 hr. Among test disinfectant solutions, hydrogen peroxide showed the highest $LC_50$ in flounder (201.3), rockfish (269.7), and black sea bream (139.3 ppm). DDAC revealed the lowest $LC_{50}$ in flounder (2.1), rockfish (1.0), and black sea bream (1.5 ppm). These results suggest that DDAC, quaternary ammonium compounds, glutaraldehyde, and sodium hypochlorite are effective disinfectants for fish and bacterial species examined in this study.

• Journal of Food Hygiene and Safety
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• v.32 no.6
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• pp.507-512
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• 2017

There has been increasing concern regarding misuse of disinfectants and sanitizers such as ethanol, sodium hypochlorite, and hydrogen peroxide for food contact surfaces in the food industry. Examining the efficacy of the concentration of currently used disinfectants and sanitizers is urgently required in the Korean society. This study aimed to develop predictive reduction models for Escherichia coli and Staphylococcus aureus in suspension, as a function of $ClO_2$ (chlorine dioxide) and contact time using response surface methodology. E. coli ATCC 10536 and S. aureus ATCC 6538 (initial inoculum, 8-9 log CFU/mL) in tryptic soy broth were treated with different concentrations of $ClO_2$ (5, 20, and 35 ppm) for different contact times (1, 3, and 5 min) following a central composite design. The polynomial reduction models for $ClO_2$ on E. coli and S. aureus were developed under the clean condition. E. coli reduction by 35 ppm $ClO_2$ for 1, 3, and 5 min was 2.49, 2.70, and 3.65 log CFU/mL, respectively. Also, S. aureus reduction by 35 ppm $ClO_2$ for 1, 3, and 5 min was 4.59, 5.25, and 5.81 log CFU/mL, respectively. The predictive response polynomial models developed were $R=0.43231-0.056492^*X_1-0.097771^*X_2+9.24167E-003^*X_1^*X_2+3.06333E-003^*X_1{^2}$ ($R^2=0.98$) on E. coli and $R=1.10542-0.20896^*X_1-0.046062^*X_2+8.30000E-003^*X_1^*X_2+8.73300E-003^*X_1{^2}$ ($R^2=0.99$) on S. aureus, where R was the bacterial reduction (log CFU/mL), $X_1$ was the concentration and $X_2$ was the contact time. Our predictive reduction models should be validated in developing the optimal concentration and contact time of $ClO_2$ for inhibiting E. coli and S. aureus on food contact surfaces.

• Korean Journal of Materials Research
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• v.28 no.1
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• pp.6-11
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• 2018

There are various manufacturing processes for pure $SiO_2$ that is used as abrasives, chemicals, filters, and glasses, and in metallurgy and optical industries. In the optical fiber industry, to produce $SiO_2$ preform, $SiCl_4$ is utilized as a raw material. However, the combustion reaction of $SiCl_4$ has caused critical environmental issues, such as ozone deficiency by chlorine compounds, the greenhouse effect by carbon dioxide and corrosive gas such as hydrochloric acid. Thus, finding an alternative source that does not have those environmental issues is important for the future. Octamethylcyclotetrasiloxane (OMCTS or D4) as a chlorine free source is recently promising candidate for the $SiO_2$ preform formation. In this study, we first conducted a vaporizer design to vaporize the OMCTS. The vaporizer for the OMCTS vaporization was produced on the basis of the results of the vaporizer design. The size of the primary particle of the $SiO_2$ formed by OMCTS was less than 100 nm. X-ray diffraction patterns of the $SiO_2$ indicated an amorphous phase. Fourier-transform infrared spectroscopy analysis revealed the Si-O-Si bond without the -OH group.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.4
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• pp.94-102
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• 1996

This study was accomplished to get the basic data for the optimum chemical feed, evaluating interference between tastes and odors chemicals and coagulants in existing water treatment processes. During the tastes and odors occurs at D intaking tower area in 1995, PAC(Powdered Activated Carbon) feed with coagulants was PAC feed only and with coagulant simultaneously were appeared TON removal efficiency about 84%-87% within 20 min reaction time, but feed with time intervals was about 98% TON removal efficiency. Therefore in the case of PAC feed with coagulant, it is effective to feed coagulant on some time intervals in removing tastes and odors. It is not effective to feed PAC with chlorine dioxide($ClO_2$) or chlorine simultaneously in removing tastes and odors, because these chemicals were reduced the adsorption capacity of PAC.